The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Many modern automatic transmission configurations for passenger cars and light trucks include a plurality of planetary gear assemblies arranged in tandem. Various fixed members as well as selectively engageable clutches and brakes connect elements of the planetary gear assemblies to provide a sequence of gear ratios or speeds.
An integral part of these automatic transmission configurations is a torque converter, a fluid filled device that not only multiplies engine torque but also acts as a fluid coupling between the engine and transmission which disconnects the engine output from the transmission input at engine idle.
While the disconnection provided by a torque converter is a necessity, there have long been raised questions about the efficiency and cost of this device, primarily relating to the nature of the coupling between the engine output and the transmission input the torque converter provides. One improvement, adopted many years ago is the lock-up torque converter. In this device, when the torque converter (and entire powertrain) reaches a certain speed, the input and the output of the torque converter are locked together, thereby eliminating any fluid (frictional) losses between the input and the output of the torque converter. Nonetheless, this device still represents a significantly complex and expensive powertrain component and efforts to improve the selective torque coupling between the engine output and the transmission input continue.
The present invention is so directed.